The present invention relates to low flammability, hot storable and nondeflagrating powder pigment preparations.
Many commercially available powder pigments have a burning time of less than 45 seconds for 100 mm, requiring them to be classified as a dangerous goods under current statutory guidelines. The handling and storing of such substances is therefore subject to special safety regulations, which usually necessitate very costly equipment and building measures.
DD 250 322 A1 discloses plastic molding compositions containing flame retardant pigments where the pigment is a crystalline nitridophosphate said to possess flame retardant properties. Ammonium polyphosphate (APP) is used for flameproofing plastics (DE-A1-30 05 252, EP-A-0 049 763), but it has a significant effect on the material properties of the surrounding medium.
There is hitherto no known method for improving the safety of organic powder pigments without impairing the material properties.
The present invention therefore has for its object to provide flameproofed or low flammability organic powder pigments without significant impairment of the pigmentary properties, the color properties, the rheology or the dispersibility.
It has been determined that this object is surprisingly achieved by a pigment preparation consisting essentially of the organic pigment and an ammonium polyphosphate or an organophosphorus compound.
The present invention accordingly provides a pigment preparation comprising an organic pigment and 0.2 to 20% by weight, preferably 1 to 15% by weight, especially 2 to 10% by weight, based on the total weight of the pigment preparation, of an ammonium polyphosphate (APP) or of an organophosphorus compound.
APPs for the purposes of the present invention include those of the general formula
H(nxe2x88x92m)+2 (NH4)mPnO3n+1
where n is an integer having an average of about 20 to 800 and the ratio of m to n is between 0.7 and 1.1 (DE-A-12 83 532); also microencapsulated APP, preferably comprising 75 to 99% by weight of APP of the above formula and preferably 1 to 25% by weight of a synthetic resin surrounding the individual APP particles, which synthetic resin may be composed of melamine and formaldehyde (EP-A-0 033 361); or of phenol and formaldehyde (DE-A-30 05 252); or of melamine and/or dicyandiamide (EP-A-0 106 248); of polyurea (EP-A-0 180 790), of polyurethane (EP-A-0 178 554) or of polycarbodiimide (EP-A-0 178 529).
APP itself can be prepared according to known processes, for example as described in U.S. Pat. No. 3 978 195, EP-A-0 480 180, EP-A-0 537 475, EP-A-0 411 381 or EP-A-0 088 265.
The above-described APPs are also commercially available under the name of (copyright)Exolit (Clariant GmbH), eg. Exolit AP 422, Exolit AP 423, Exolit AP 452, Exolit AP 462.
Organophosphorus compounds for the purposes of the present invention are for example tris(2-chloroethyl) phosphate, tris(2-isopropyl) phosphate, (5-ethyl-2-methyl-1,3,2-dioxaphosphorinan-5-yl)methyl methyl methanephosphonate, phosphoric acid ethylene glycol polyester with hydroxyalkyl ester and alkyl ester groups or with hydroxyalkyl ester and chloroalkyl ester groups, eg. Exolit OP 514, Exolit OP 550, Exolit OP 910.
Useful organic pigments include for example azo pigments, such as monoazo, disazo, naphtol, azo condensation or metal complex pigments, and also polycyclic pigments, such as isoindolinone and isoindoline pigments, anthanthrone, thioindigo, quinophthalone, anthraquinone, dioxazine, phthalocyanine, quinacridone, perylene, perinone, diketopyrrolopyrrole, thiazoindigo and azomethine pigments.
Of particular interest are those organic pigments whose powders are readily combustible, for example C.I. Pigment Red 38, P. Red 184, P. Yellow 12, P. Orange 5.
The pigment preparation of the invention may further comprise customary assistants and additives, eg. dispersants, extenders, waxes, fillers, standardizers, defoamers, antidusters, shading colorants, surfactants, preservatives and drying retarders.
Of particular interest are pigment preparations consisting essentially of 0.2 to 20% by weight, preferably 1 to 15% by weight, especially 2 to 10% by weight, of an ammonium polyphosphate or of an organophosphorus compound; 99.8 to 80% by weight, preferably 99 to 85% by weight, especially 98 to 90% by weight, of an organic pigment; and 0 to 15% by weight, for example 0.1 to 10% by weight, of said assistants and additives; based on the total weight (100%) of the pigment preparation.
The pigment preparation of the invention can be prepared by mixing the organic pigment in the form of the pulverulent pigment or of a water-moist filter or press cake or of a pigment suspension with the APP or the organophosphorus compound in powder form or in the form of a solution or suspension in water, in the abovementioned mixing ratios, for example with the aid of a powder mixer or paste mixer.
The pigment preparations of the invention can be present in granular, microgranular or pulverulent form.
By adding APP, the invention changes the burning characteristics of readily combustible pigment powders to the effect that the flame self-extinguishes shortly after being lit. There is thus no reason to classify them as dangerous goods. By adding APP, the invention changes the dust explosion capability to the effect that the pressure rise rate (KST value) is greatly reduced and the minimum ignition energies of practically relevant dust-air mixtures are higher by 1 to 2 orders of magnitude.
The pigment preparations prepared according to the invention are useful for pigmenting macromolecular organic materials of natural or synthetic origin, for example plastics, resins, varnishes, paints or electrophotographic toners and developers and also inks, including printing inks.
Macromolecular organic materials pigmentable using the pigment preparations mentioned include for example cellulose ethers and esters, such as ethylcellulose, nitrocellulose, cellulose acetate or cellulose butyrate, natural resins or synthetic resins, such as addition polymerization resins or condensation resins, for example amino resins, especially urea- and melamine-formaldehyde resins, alkyd resins, acrylic resins, phenolic resins, polycarbonates, polyolefins, such as polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyacrylonitrile, polyacrylic esters, polyamides, polyurethanes or polyesters, rubber, casein, silicone and silicone resins, individually or mixtures.
It is immaterial in this connection whether the macromolecular organic compounds mentioned are present as plastically deformable compositions, melts or in the form of dopes, coatings, paints or printing inks. Depending on the application, it is advantageous to use the pigment preparations of the invention as a blend or in the form of preparations or dispersions. Based on the macromolecular organic material to be pigmented, the pigment preparations of the invention are used in an amount of preferably 0.05 to 30% by weight, preferably 0.1 to 10% by weight.
The pigment preparations of the invention are also useful as colorants in electrophotographic toners and developers, for example one- or two-component powder toners (also known as one- or two-component developers), magnetic toners, liquid toners, addition polymerization toners and also specialty toners (L. B. Schein, xe2x80x9cElectrophotography and Development Physicsxe2x80x9d; Springer Series in Electrophysics 14, Springer Verlag, 2nd edition, 1992).
Typical toner binders are addition polymerization, polyaddition and polycondensation resins, such as styrene, styrene-acrylate, styrene-butadiene, acrylate, polyester, phenol-epoxide resins, polysulfones, polyurethanes, individually or in combination, and also polyethylene and polypropylene, which may each include further ingredients, such as charge control agents, waxes or flow assistants, or are subsequently modified with these additives.
The pigment preparations of the invention are further useful as colorants in powders and powder coatings, especially in triboelectrically or electrokinetically sprayable powder coatings used for surface coating of objects composed for example of metal, wood, plastic, glass, ceramic, concrete, textile material, paper or rubber (J .F. Hughes, xe2x80x9cElectrostatics Powder Coatingxe2x80x9d Research Studies, John Wiley and Sons, 1984).
Powder coating resins used are typically epoxy resins, carboxyl- and hydroxyl-containing polyester resins, polyurethane and acrylic resins together with customary hardeners. Combinations of resins are also used. For instance, epoxy resins combined with carboxyl- and hydroxyl-containing polyester resins are frequently used. Typical hardener components (depending on the resin system) include for example acid anhydride, imidazoles and also dicyandiamide and derivatives thereof, capped isocyanates, bisacylurethanes, phenolic and melamine resins, triglycidyl isocyanurates, oxazolines and dicarboxylic acids.
The pigment preparations of the invention are also useful as colorants in ink-jet inks based on aqueous and nonaqueous systems and also in inks processed by the hot-melt method.
The pigment preparations of the invention are further useful as colorants for color filters and also for additive as well as subtractive color production.